Protective device for vacuum tubes



1957 s. KUCHINSKY 2,804,568

PROTECTIVE DEVICE FOR VACUUM TUBES Filed Aug. 15, 1955 INVENTOR. 'SAU L KUCHINSKY ATTORNEY United States Patent PROTECTIVE DEVICE FOR VACUUM TUBES Saul Kuchinsky, Phoenixville, Pa.,, assignor to Burroughs CorporatiomDetroit, Mich., a corporation of Michigan Application August 15, 1955, Serial No. 528,459

7 Claims. (Cl. 313-312) The present invention relates to means for improving the reliability of operation of magnetron beam switching tube assemblies.

In the field use of magnetron beam switching tubes, which have been potted in an individual magnet, it has been found on some occasions that such tubes develop unexplainable variation of operating characteristics. For a considerable period of time this was believed to be due to poor tube characteristics and therefore resulted in a long series of expensive investigations without finding any tube difliculty. However, eventually it was found that changes in the magnetic field strength caused the inaccurate and disturbing operation results, even though such tubes were delivered precision tested for a uniform magnetic field. Accordingly it was apparent that the change in field strength occurred in the subsequent handling of the tubes. Finally it was determined that the trouble lay in damage to the magnet by shock and in most cases was traced as the result of striking of the magnet with a ferromagnetic tool which was brought close enough to be drawn into physical contact with the magnet.

An object of the present invention is to provide an improved beam switching tube assembly capable of withstanding all of the hazards of field use.

Another object is to provide means for projecting beam switching tubes from blows, shocks or careless handling of such tubes in field use.

According to the present invention, therefore, shock absorbing caps or protective covers are provided for the ends of the magnet in which the beam tube is assembled to thereby maintain a physical spacing from the ends of the magnet and to cushion physical impact in the event a ferromagnetic object is brought within the field of the magnet.

Other improvements and features of the invention will hereinafter appear throughout the detailed description.

In the accompanying drawings- Fig. 1 is an exploded view in perspective of a beam switching tube embodying one form of the present invention;

Fig. 2 is a side elevation view of the assembled tube;

Fig. 3 is a view of one end of the tube; and

Fig. 4 is a view of the other end of the tube of Fig. 2.

Referring to the drawings a magnetron beam switching tube is shown which employs the usual high vacuum and beam forming properties of crossed electric and magnetic fields. The axial magnetic field is provided by a cylindrical magnet 11 attached permanently by a plotting compound 25 around the glass envelope of the tube. The magnet leaves opposite ends 16 and of the tube exposed primarily for tube mounting.

For the purpose of protecting the magnet from blows or shocks which cause weakening or other disturbance of the magnetic field, the ends of the magnet 11 are protected by cushioning means, which in the preferred form, are two plastic end caps 12 and 13 arranged respectively Patented Aug. 27, 1957 to seat snugly over the magnet ends and extend sufiiciently along the cylindrical body to give the desired protection to the magnet 10. Both caps 12 and 13 are formed of non-magnetic material, and preferably in the present instance, of plastic material molded into a shape complemental to the magnet ends and of sutficient thickness and resilience to act as a cushion should the magnet be'struck by a metal tool or otherwise. 7

The cap 12 has an annular face 14 forming an opening 15 which encircles the exposed end of the tube envelope 16, while the inner circumference of the face 14 seats against the nearest end of the magnet.

The cap 13 also has an annular face 17 forming an opening 18 which encircles the exposed prong end 20 of the tube, while the inner circumference of the face 17 seats against the nearest end of the magnet.

Since generally this type of magnet is of uniform diameter the two caps 12 and 13 serve interchangeably for the magnet ends, thereby eliminating the expense of fabricating two caps of different dimensions. When assembled for shipment as well as for use, each cap has become apermanently attached part of the magnet by reason of the gripping action of the cap body. This action is due to the diameter of the cap body which is made slightly less than the diameter of the tube so that in pressing the cap over the magnet end the resilience of the plastic allows the cap to expand for gripping telescopic assembly.

It will now be apparent that a novel protecting means for the magnet of housed beam switching tubes has been devised wherein the exposed end portions of the length of the magnet which produce the field are covered by the cap body, also the annular end face of the magnet, as well as the circumferential face edge are fully protected. Thus side, end or edge blows to the tube which are encouraged by attraction of the field upon ferromagnetic objects are absorbed without disturbance to the magnetic field. Since no substantial magnetic field emanates from the central magnet portion it becomes unnecessary to protect the full magnet body.

What is claimed is:

1. A protective device having a cylindrical magnet encircling an electronic tube, comprising a resilient shock absorbing non-magnetic cap received and fitted about an end of the magnet, and having an apertured top exposing an end of the electronic tube.

2. A protective device according to claim 1, wherein the cap is formed of molded plastic in a form complementary to that of the cylindrical magnet and has an inner diameter slightly less than the outer diameter of the magnet to thereby firmly grip the magnet by frictional contact.

3. A protective device having a cylindrical magnet encircling an electronic tube comprising two non-mag netic caps of shock absorbing material respectively received and fitted about the ends of the magnet, both caps having an apertured top to expose the respective ends of the tube mounted in the magnet.

4. A protective assembly, comprising the combination of an electron tube, a cylindrical magnet mounted about said tube and shorter than said tube to leave one end of the tube projecting, and a cap of shock absorbing material fitted over the magnet end, the top of said cap seating against the juxtaposed end of the magnet, and said top having an opening encircling said tube projection.

5. A protective assembly comprising the combination of an electronic tube, a cylindrical magnet mounted about said tube and shorter than said tube to leave both ends of the tube projecting, and apertured caps of shock absorbing material fitted respectively over the magnet ends and seating respectively against the magnet to encircle the projecting ends of the tube.

6. A protective magnetron tube assembly comprising in combination, an electronic tube, a cylindrical magnet, means mounting the tube in said cylindrical magnet, and a shock absorbing covering about at least one end of said cylindrical magnet to prevent a change in magnetic field characteristics caused by attraction of a ferromagnetic object into physical contact with the end of said magnet.

7. An electronic switching unit comprising the combination of a circuit switching tube, a cylindrical magnet 4 encircling said tube, a cushioning compound between said magnet and said tube, and a shock absorbing member telescopically fitted about said magnet.

References Cited in the file of this patent UNITED STATES PATENTS 2,187,171 Okabe Ian. 16, 1940 2,473,567 Brown June 21, 1949 2,507,331 Bertein et al. May 9, 1950 2,712,097 Auwarter June 28, 1955 2,719,267 Kunz et a1. Sept. 27, 1955 

